Water flow in the soil-plant domain. New tools and methods
Water flow in the soil-plant-atmosphere continuum (SPAC) is con- trolled by a handful of key features. On the plant side, the leaf stom- atal conductance controls the total amount of water transpired while the root axial and radial hydraulic properties defines the distribution of uptake sites in the soil domain. On the soil side, the soil hydraulic properties (retention capacity and conductivity) and the 3D distri- bution of water define the quantity of water available to the plant. The explicit integration of these factors is required to decrypt their quantitative influence in the uptake process at the plant scale.
In this work, different tools were developed to facilitate the obser- vation and analysis of water flows in the SPAC from different points of view. Firstly, a new root image analysis software, SmartRoot, was created to enable a quantitative analysis of root system architecture. Secondly, the creation of an experimental platform made possible the parallel monitoring of soil water content and root architecture of 20 plants. Finally, the implementation of a new functional-structural plant model, PlaNet-Maize , allowed the simulation of water flow reg- ulation at the plant level with a resolution down to the organ.
Using these new tools, the quantitative influence of several root features on the water uptake processes was evaluated. Firstly, deep- rooted plants were shown, not only to be able to access water more deeply in the profile, but also to ensure a better distribution of the water content decrease in the soil profile. Secondly, the regulation of root axial and radial hydraulic properties were shown to influence the uptake process at the plant scale, although in a smaller extent com- pared to the control of water flow by the stomata. Root features most probably ensure a fine regulation of the flow in response to changes in the soil environment and may be important in securing soil water supply in vulnerable rhizospheric compartments.
In conclusion, the successful development of new tools and meth- ods allowed a more detailed analysis of the influence of several plant features in the water uptake process.